quick plumbing question

[apexifd]

I know that I can probably find the answer to this somewhere online, but sometimes it's just easier to ask people who knows.

I am attempting my first ever plumbing job. set up is a 75gallon RR with 1.5" pre drill holes. and a 33 gal sump. I have 3/4" pvc and a few elbows.


my questions are:

1: will 3/4" pvc too small and restricted too much of flow?

2: should I installed a gate valve or two?

3: union for easy removals later??


thanks

Peter Yu